1 //===--- Mangle.cpp - Mangle C++ Names --------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Implements generic name mangling support for blocks and Objective-C.
10 //
11 //===----------------------------------------------------------------------===//
12 #include "clang/AST/Attr.h"
13 #include "clang/AST/ASTContext.h"
14 #include "clang/AST/Decl.h"
15 #include "clang/AST/DeclCXX.h"
16 #include "clang/AST/DeclObjC.h"
17 #include "clang/AST/DeclTemplate.h"
18 #include "clang/AST/ExprCXX.h"
19 #include "clang/AST/Mangle.h"
20 #include "clang/AST/VTableBuilder.h"
21 #include "clang/Basic/ABI.h"
22 #include "clang/Basic/SourceManager.h"
23 #include "clang/Basic/TargetInfo.h"
24 #include "llvm/ADT/StringExtras.h"
25 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/Mangler.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/Format.h"
29 #include "llvm/Support/raw_ostream.h"
30 
31 using namespace clang;
32 
33 // FIXME: For blocks we currently mimic GCC's mangling scheme, which leaves
34 // much to be desired. Come up with a better mangling scheme.
35 
36 static void mangleFunctionBlock(MangleContext &Context,
37                                 StringRef Outer,
38                                 const BlockDecl *BD,
39                                 raw_ostream &Out) {
40   unsigned discriminator = Context.getBlockId(BD, true);
41   if (discriminator == 0)
42     Out << "__" << Outer << "_block_invoke";
43   else
44     Out << "__" << Outer << "_block_invoke_" << discriminator+1;
45 }
46 
47 void MangleContext::anchor() { }
48 
49 enum CCMangling {
50   CCM_Other,
51   CCM_Fast,
52   CCM_RegCall,
53   CCM_Vector,
54   CCM_Std,
55   CCM_WasmMainArgcArgv
56 };
57 
58 static bool isExternC(const NamedDecl *ND) {
59   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND))
60     return FD->isExternC();
61   if (const VarDecl *VD = dyn_cast<VarDecl>(ND))
62     return VD->isExternC();
63   return false;
64 }
65 
66 static CCMangling getCallingConvMangling(const ASTContext &Context,
67                                          const NamedDecl *ND) {
68   const TargetInfo &TI = Context.getTargetInfo();
69   const llvm::Triple &Triple = TI.getTriple();
70 
71   // On wasm, the argc/argv form of "main" is renamed so that the startup code
72   // can call it with the correct function signature.
73   // On Emscripten, users may be exporting "main" and expecting to call it
74   // themselves, so we can't mangle it.
75   if (Triple.isWasm() && !Triple.isOSEmscripten())
76     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND))
77       if (FD->isMain() && FD->hasPrototype() && FD->param_size() == 2)
78         return CCM_WasmMainArgcArgv;
79 
80   if (!Triple.isOSWindows() || !Triple.isX86())
81     return CCM_Other;
82 
83   if (Context.getLangOpts().CPlusPlus && !isExternC(ND) &&
84       TI.getCXXABI() == TargetCXXABI::Microsoft)
85     return CCM_Other;
86 
87   const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND);
88   if (!FD)
89     return CCM_Other;
90   QualType T = FD->getType();
91 
92   const FunctionType *FT = T->castAs<FunctionType>();
93 
94   CallingConv CC = FT->getCallConv();
95   switch (CC) {
96   default:
97     return CCM_Other;
98   case CC_X86FastCall:
99     return CCM_Fast;
100   case CC_X86StdCall:
101     return CCM_Std;
102   case CC_X86VectorCall:
103     return CCM_Vector;
104   }
105 }
106 
107 bool MangleContext::shouldMangleDeclName(const NamedDecl *D) {
108   const ASTContext &ASTContext = getASTContext();
109 
110   CCMangling CC = getCallingConvMangling(ASTContext, D);
111   if (CC != CCM_Other)
112     return true;
113 
114   // If the declaration has an owning module for linkage purposes that needs to
115   // be mangled, we must mangle its name.
116   if (!D->hasExternalFormalLinkage() && D->getOwningModuleForLinkage())
117     return true;
118 
119   // In C, functions with no attributes never need to be mangled. Fastpath them.
120   if (!getASTContext().getLangOpts().CPlusPlus && !D->hasAttrs())
121     return false;
122 
123   // Any decl can be declared with __asm("foo") on it, and this takes precedence
124   // over all other naming in the .o file.
125   if (D->hasAttr<AsmLabelAttr>())
126     return true;
127 
128   // Declarations that don't have identifier names always need to be mangled.
129   if (isa<MSGuidDecl>(D))
130     return true;
131 
132   return shouldMangleCXXName(D);
133 }
134 
135 void MangleContext::mangleName(GlobalDecl GD, raw_ostream &Out) {
136   const NamedDecl *D = cast<NamedDecl>(GD.getDecl());
137   // Any decl can be declared with __asm("foo") on it, and this takes precedence
138   // over all other naming in the .o file.
139   if (const AsmLabelAttr *ALA = D->getAttr<AsmLabelAttr>()) {
140     // If we have an asm name, then we use it as the mangling.
141 
142     // If the label isn't literal, or if this is an alias for an LLVM intrinsic,
143     // do not add a "\01" prefix.
144     if (!ALA->getIsLiteralLabel() || ALA->getLabel().startswith("llvm.")) {
145       Out << ALA->getLabel();
146       return;
147     }
148 
149     // Adding the prefix can cause problems when one file has a "foo" and
150     // another has a "\01foo". That is known to happen on ELF with the
151     // tricks normally used for producing aliases (PR9177). Fortunately the
152     // llvm mangler on ELF is a nop, so we can just avoid adding the \01
153     // marker.
154     char GlobalPrefix =
155         getASTContext().getTargetInfo().getDataLayout().getGlobalPrefix();
156     if (GlobalPrefix)
157       Out << '\01'; // LLVM IR Marker for __asm("foo")
158 
159     Out << ALA->getLabel();
160     return;
161   }
162 
163   if (auto *GD = dyn_cast<MSGuidDecl>(D))
164     return mangleMSGuidDecl(GD, Out);
165 
166   const ASTContext &ASTContext = getASTContext();
167   CCMangling CC = getCallingConvMangling(ASTContext, D);
168 
169   if (CC == CCM_WasmMainArgcArgv) {
170     Out << "__main_argc_argv";
171     return;
172   }
173 
174   bool MCXX = shouldMangleCXXName(D);
175   const TargetInfo &TI = Context.getTargetInfo();
176   if (CC == CCM_Other || (MCXX && TI.getCXXABI() == TargetCXXABI::Microsoft)) {
177     if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(D))
178       mangleObjCMethodNameAsSourceName(OMD, Out);
179     else
180       mangleCXXName(GD, Out);
181     return;
182   }
183 
184   Out << '\01';
185   if (CC == CCM_Std)
186     Out << '_';
187   else if (CC == CCM_Fast)
188     Out << '@';
189   else if (CC == CCM_RegCall)
190     Out << "__regcall3__";
191 
192   if (!MCXX)
193     Out << D->getIdentifier()->getName();
194   else if (const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(D))
195     mangleObjCMethodNameAsSourceName(OMD, Out);
196   else
197     mangleCXXName(GD, Out);
198 
199   const FunctionDecl *FD = cast<FunctionDecl>(D);
200   const FunctionType *FT = FD->getType()->castAs<FunctionType>();
201   const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(FT);
202   if (CC == CCM_Vector)
203     Out << '@';
204   Out << '@';
205   if (!Proto) {
206     Out << '0';
207     return;
208   }
209   assert(!Proto->isVariadic());
210   unsigned ArgWords = 0;
211   if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD))
212     if (!MD->isStatic())
213       ++ArgWords;
214   for (const auto &AT : Proto->param_types())
215     // Size should be aligned to pointer size.
216     ArgWords +=
217         llvm::alignTo(ASTContext.getTypeSize(AT), TI.getPointerWidth(0)) /
218         TI.getPointerWidth(0);
219   Out << ((TI.getPointerWidth(0) / 8) * ArgWords);
220 }
221 
222 void MangleContext::mangleMSGuidDecl(const MSGuidDecl *GD, raw_ostream &Out) {
223   // For now, follow the MSVC naming convention for GUID objects on all
224   // targets.
225   MSGuidDecl::Parts P = GD->getParts();
226   Out << llvm::format("_GUID_%08" PRIx32 "_%04" PRIx32 "_%04" PRIx32 "_",
227                       P.Part1, P.Part2, P.Part3);
228   unsigned I = 0;
229   for (uint8_t C : P.Part4And5) {
230     Out << llvm::format("%02" PRIx8, C);
231     if (++I == 2)
232       Out << "_";
233   }
234 }
235 
236 void MangleContext::mangleGlobalBlock(const BlockDecl *BD,
237                                       const NamedDecl *ID,
238                                       raw_ostream &Out) {
239   unsigned discriminator = getBlockId(BD, false);
240   if (ID) {
241     if (shouldMangleDeclName(ID))
242       mangleName(ID, Out);
243     else {
244       Out << ID->getIdentifier()->getName();
245     }
246   }
247   if (discriminator == 0)
248     Out << "_block_invoke";
249   else
250     Out << "_block_invoke_" << discriminator+1;
251 }
252 
253 void MangleContext::mangleCtorBlock(const CXXConstructorDecl *CD,
254                                     CXXCtorType CT, const BlockDecl *BD,
255                                     raw_ostream &ResStream) {
256   SmallString<64> Buffer;
257   llvm::raw_svector_ostream Out(Buffer);
258   mangleName(GlobalDecl(CD, CT), Out);
259   mangleFunctionBlock(*this, Buffer, BD, ResStream);
260 }
261 
262 void MangleContext::mangleDtorBlock(const CXXDestructorDecl *DD,
263                                     CXXDtorType DT, const BlockDecl *BD,
264                                     raw_ostream &ResStream) {
265   SmallString<64> Buffer;
266   llvm::raw_svector_ostream Out(Buffer);
267   mangleName(GlobalDecl(DD, DT), Out);
268   mangleFunctionBlock(*this, Buffer, BD, ResStream);
269 }
270 
271 void MangleContext::mangleBlock(const DeclContext *DC, const BlockDecl *BD,
272                                 raw_ostream &Out) {
273   assert(!isa<CXXConstructorDecl>(DC) && !isa<CXXDestructorDecl>(DC));
274 
275   SmallString<64> Buffer;
276   llvm::raw_svector_ostream Stream(Buffer);
277   if (const ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(DC)) {
278     mangleObjCMethodNameAsSourceName(Method, Stream);
279   } else {
280     assert((isa<NamedDecl>(DC) || isa<BlockDecl>(DC)) &&
281            "expected a NamedDecl or BlockDecl");
282     if (isa<BlockDecl>(DC))
283       for (; DC && isa<BlockDecl>(DC); DC = DC->getParent())
284         (void) getBlockId(cast<BlockDecl>(DC), true);
285     assert((isa<TranslationUnitDecl>(DC) || isa<NamedDecl>(DC)) &&
286            "expected a TranslationUnitDecl or a NamedDecl");
287     if (const auto *CD = dyn_cast<CXXConstructorDecl>(DC))
288       mangleCtorBlock(CD, /*CT*/ Ctor_Complete, BD, Out);
289     else if (const auto *DD = dyn_cast<CXXDestructorDecl>(DC))
290       mangleDtorBlock(DD, /*DT*/ Dtor_Complete, BD, Out);
291     else if (auto ND = dyn_cast<NamedDecl>(DC)) {
292       if (!shouldMangleDeclName(ND) && ND->getIdentifier())
293         Stream << ND->getIdentifier()->getName();
294       else {
295         // FIXME: We were doing a mangleUnqualifiedName() before, but that's
296         // a private member of a class that will soon itself be private to the
297         // Itanium C++ ABI object. What should we do now? Right now, I'm just
298         // calling the mangleName() method on the MangleContext; is there a
299         // better way?
300         mangleName(ND, Stream);
301       }
302     }
303   }
304   mangleFunctionBlock(*this, Buffer, BD, Out);
305 }
306 
307 void MangleContext::mangleObjCMethodName(const ObjCMethodDecl *MD,
308                                          raw_ostream &OS,
309                                          bool includePrefixByte,
310                                          bool includeCategoryNamespace) {
311   if (getASTContext().getLangOpts().ObjCRuntime.isGNUFamily()) {
312     // This is the mangling we've always used on the GNU runtimes, but it
313     // has obvious collisions in the face of underscores within class
314     // names, category names, and selectors; maybe we should improve it.
315 
316     OS << (MD->isClassMethod() ? "_c_" : "_i_")
317        << MD->getClassInterface()->getName() << '_';
318 
319     if (includeCategoryNamespace) {
320       if (auto category = MD->getCategory())
321         OS << category->getName();
322     }
323     OS << '_';
324 
325     auto selector = MD->getSelector();
326     for (unsigned slotIndex = 0,
327                   numArgs = selector.getNumArgs(),
328                   slotEnd = std::max(numArgs, 1U);
329            slotIndex != slotEnd; ++slotIndex) {
330       if (auto name = selector.getIdentifierInfoForSlot(slotIndex))
331         OS << name->getName();
332 
333       // Replace all the positions that would've been ':' with '_'.
334       // That's after each slot except that a unary selector doesn't
335       // end in ':'.
336       if (numArgs)
337         OS << '_';
338     }
339 
340     return;
341   }
342 
343   // \01+[ContainerName(CategoryName) SelectorName]
344   if (includePrefixByte) {
345     OS << '\01';
346   }
347   OS << (MD->isInstanceMethod() ? '-' : '+') << '[';
348   if (const auto *CID = MD->getCategory()) {
349     OS << CID->getClassInterface()->getName();
350     if (includeCategoryNamespace) {
351       OS << '(' << *CID << ')';
352     }
353   } else if (const auto *CD =
354                  dyn_cast<ObjCContainerDecl>(MD->getDeclContext())) {
355     OS << CD->getName();
356   } else {
357     llvm_unreachable("Unexpected ObjC method decl context");
358   }
359   OS << ' ';
360   MD->getSelector().print(OS);
361   OS << ']';
362 }
363 
364 void MangleContext::mangleObjCMethodNameAsSourceName(const ObjCMethodDecl *MD,
365                                                      raw_ostream &Out) {
366   SmallString<64> Name;
367   llvm::raw_svector_ostream OS(Name);
368 
369   mangleObjCMethodName(MD, OS, /*includePrefixByte=*/false,
370                        /*includeCategoryNamespace=*/true);
371   Out << OS.str().size() << OS.str();
372 }
373 
374 class ASTNameGenerator::Implementation {
375   std::unique_ptr<MangleContext> MC;
376   llvm::DataLayout DL;
377 
378 public:
379   explicit Implementation(ASTContext &Ctx)
380       : MC(Ctx.createMangleContext()), DL(Ctx.getTargetInfo().getDataLayout()) {
381   }
382 
383   bool writeName(const Decl *D, raw_ostream &OS) {
384     // First apply frontend mangling.
385     SmallString<128> FrontendBuf;
386     llvm::raw_svector_ostream FrontendBufOS(FrontendBuf);
387     if (auto *FD = dyn_cast<FunctionDecl>(D)) {
388       if (FD->isDependentContext())
389         return true;
390       if (writeFuncOrVarName(FD, FrontendBufOS))
391         return true;
392     } else if (auto *VD = dyn_cast<VarDecl>(D)) {
393       if (writeFuncOrVarName(VD, FrontendBufOS))
394         return true;
395     } else if (auto *MD = dyn_cast<ObjCMethodDecl>(D)) {
396       MC->mangleObjCMethodName(MD, OS, /*includePrefixByte=*/false,
397                                /*includeCategoryNamespace=*/true);
398       return false;
399     } else if (auto *ID = dyn_cast<ObjCInterfaceDecl>(D)) {
400       writeObjCClassName(ID, FrontendBufOS);
401     } else {
402       return true;
403     }
404 
405     // Now apply backend mangling.
406     llvm::Mangler::getNameWithPrefix(OS, FrontendBufOS.str(), DL);
407     return false;
408   }
409 
410   std::string getName(const Decl *D) {
411     std::string Name;
412     {
413       llvm::raw_string_ostream OS(Name);
414       writeName(D, OS);
415     }
416     return Name;
417   }
418 
419   enum ObjCKind {
420     ObjCClass,
421     ObjCMetaclass,
422   };
423 
424   static StringRef getClassSymbolPrefix(ObjCKind Kind,
425                                         const ASTContext &Context) {
426     if (Context.getLangOpts().ObjCRuntime.isGNUFamily())
427       return Kind == ObjCMetaclass ? "_OBJC_METACLASS_" : "_OBJC_CLASS_";
428     return Kind == ObjCMetaclass ? "OBJC_METACLASS_$_" : "OBJC_CLASS_$_";
429   }
430 
431   std::vector<std::string> getAllManglings(const ObjCContainerDecl *OCD) {
432     StringRef ClassName;
433     if (const auto *OID = dyn_cast<ObjCInterfaceDecl>(OCD))
434       ClassName = OID->getObjCRuntimeNameAsString();
435     else if (const auto *OID = dyn_cast<ObjCImplementationDecl>(OCD))
436       ClassName = OID->getObjCRuntimeNameAsString();
437 
438     if (ClassName.empty())
439       return {};
440 
441     auto Mangle = [&](ObjCKind Kind, StringRef ClassName) -> std::string {
442       SmallString<40> Mangled;
443       auto Prefix = getClassSymbolPrefix(Kind, OCD->getASTContext());
444       llvm::Mangler::getNameWithPrefix(Mangled, Prefix + ClassName, DL);
445       return std::string(Mangled.str());
446     };
447 
448     return {
449         Mangle(ObjCClass, ClassName),
450         Mangle(ObjCMetaclass, ClassName),
451     };
452   }
453 
454   std::vector<std::string> getAllManglings(const Decl *D) {
455     if (const auto *OCD = dyn_cast<ObjCContainerDecl>(D))
456       return getAllManglings(OCD);
457 
458     if (!(isa<CXXRecordDecl>(D) || isa<CXXMethodDecl>(D)))
459       return {};
460 
461     const NamedDecl *ND = cast<NamedDecl>(D);
462 
463     ASTContext &Ctx = ND->getASTContext();
464     std::unique_ptr<MangleContext> M(Ctx.createMangleContext());
465 
466     std::vector<std::string> Manglings;
467 
468     auto hasDefaultCXXMethodCC = [](ASTContext &C, const CXXMethodDecl *MD) {
469       auto DefaultCC = C.getDefaultCallingConvention(/*IsVariadic=*/false,
470                                                      /*IsCXXMethod=*/true);
471       auto CC = MD->getType()->castAs<FunctionProtoType>()->getCallConv();
472       return CC == DefaultCC;
473     };
474 
475     if (const auto *CD = dyn_cast_or_null<CXXConstructorDecl>(ND)) {
476       Manglings.emplace_back(getMangledStructor(CD, Ctor_Base));
477 
478       if (Ctx.getTargetInfo().getCXXABI().isItaniumFamily())
479         if (!CD->getParent()->isAbstract())
480           Manglings.emplace_back(getMangledStructor(CD, Ctor_Complete));
481 
482       if (Ctx.getTargetInfo().getCXXABI().isMicrosoft())
483         if (CD->hasAttr<DLLExportAttr>() && CD->isDefaultConstructor())
484           if (!(hasDefaultCXXMethodCC(Ctx, CD) && CD->getNumParams() == 0))
485             Manglings.emplace_back(getMangledStructor(CD, Ctor_DefaultClosure));
486     } else if (const auto *DD = dyn_cast_or_null<CXXDestructorDecl>(ND)) {
487       Manglings.emplace_back(getMangledStructor(DD, Dtor_Base));
488       if (Ctx.getTargetInfo().getCXXABI().isItaniumFamily()) {
489         Manglings.emplace_back(getMangledStructor(DD, Dtor_Complete));
490         if (DD->isVirtual())
491           Manglings.emplace_back(getMangledStructor(DD, Dtor_Deleting));
492       }
493     } else if (const auto *MD = dyn_cast_or_null<CXXMethodDecl>(ND)) {
494       Manglings.emplace_back(getName(ND));
495       if (MD->isVirtual())
496         if (const auto *TIV = Ctx.getVTableContext()->getThunkInfo(MD))
497           for (const auto &T : *TIV)
498             Manglings.emplace_back(getMangledThunk(MD, T));
499     }
500 
501     return Manglings;
502   }
503 
504 private:
505   bool writeFuncOrVarName(const NamedDecl *D, raw_ostream &OS) {
506     if (MC->shouldMangleDeclName(D)) {
507       GlobalDecl GD;
508       if (const auto *CtorD = dyn_cast<CXXConstructorDecl>(D))
509         GD = GlobalDecl(CtorD, Ctor_Complete);
510       else if (const auto *DtorD = dyn_cast<CXXDestructorDecl>(D))
511         GD = GlobalDecl(DtorD, Dtor_Complete);
512       else if (D->hasAttr<CUDAGlobalAttr>())
513         GD = GlobalDecl(cast<FunctionDecl>(D));
514       else
515         GD = GlobalDecl(D);
516       MC->mangleName(GD, OS);
517       return false;
518     } else {
519       IdentifierInfo *II = D->getIdentifier();
520       if (!II)
521         return true;
522       OS << II->getName();
523       return false;
524     }
525   }
526 
527   void writeObjCClassName(const ObjCInterfaceDecl *D, raw_ostream &OS) {
528     OS << getClassSymbolPrefix(ObjCClass, D->getASTContext());
529     OS << D->getObjCRuntimeNameAsString();
530   }
531 
532   std::string getMangledStructor(const NamedDecl *ND, unsigned StructorType) {
533     std::string FrontendBuf;
534     llvm::raw_string_ostream FOS(FrontendBuf);
535 
536     GlobalDecl GD;
537     if (const auto *CD = dyn_cast_or_null<CXXConstructorDecl>(ND))
538       GD = GlobalDecl(CD, static_cast<CXXCtorType>(StructorType));
539     else if (const auto *DD = dyn_cast_or_null<CXXDestructorDecl>(ND))
540       GD = GlobalDecl(DD, static_cast<CXXDtorType>(StructorType));
541     MC->mangleName(GD, FOS);
542 
543     std::string BackendBuf;
544     llvm::raw_string_ostream BOS(BackendBuf);
545 
546     llvm::Mangler::getNameWithPrefix(BOS, FOS.str(), DL);
547 
548     return BOS.str();
549   }
550 
551   std::string getMangledThunk(const CXXMethodDecl *MD, const ThunkInfo &T) {
552     std::string FrontendBuf;
553     llvm::raw_string_ostream FOS(FrontendBuf);
554 
555     MC->mangleThunk(MD, T, FOS);
556 
557     std::string BackendBuf;
558     llvm::raw_string_ostream BOS(BackendBuf);
559 
560     llvm::Mangler::getNameWithPrefix(BOS, FOS.str(), DL);
561 
562     return BOS.str();
563   }
564 };
565 
566 ASTNameGenerator::ASTNameGenerator(ASTContext &Ctx)
567     : Impl(std::make_unique<Implementation>(Ctx)) {}
568 
569 ASTNameGenerator::~ASTNameGenerator() {}
570 
571 bool ASTNameGenerator::writeName(const Decl *D, raw_ostream &OS) {
572   return Impl->writeName(D, OS);
573 }
574 
575 std::string ASTNameGenerator::getName(const Decl *D) {
576   return Impl->getName(D);
577 }
578 
579 std::vector<std::string> ASTNameGenerator::getAllManglings(const Decl *D) {
580   return Impl->getAllManglings(D);
581 }
582